1. Field of the Invention
This invention relates generally to an automatic door assembly and more particularly to apparatus for automatically controlling the operation of the automatic door.
2. Prior Art
One of the primary difficulties encountered in automatically controlling the operation of an automatic door has been the problem of preventing the door from striking an outer door frame at the end of the door stroke. It has been proposed in the art to decelerate the speed of the door at a final portion of the door stroke to stop the door exactly at the end of its stroke without substantial impact. Most of the prior art apparatus under consideration have employed limit switches for sensing the position of the door at the final portion of the door stroke to effect deceleration of the door, the limit switches being usually mounted on the outer door frame and positioned along the path of the door so that the limit-switches are actuated upon engagement with actuator means attached to the inner door frame within which a glass pane is supported. These conventional position sensing means have been found not entirely satisfactory, however, in that considerable effort is required in alignment and adjustment of the limit switches. Another disadvantage of such prior art position sensing means is that they require frequent attention and readjustment to maintain accurate operation. This difficulty arises out of the fact that the limit switches mounted on the outer door frame depend for their operation upon mechanical engagement with the actuator means.